Zanzibar: Basement Piling and Civils

Brenwal were appointed by Dandara as Principal Contractors for the groundworks and civils elements of this prestigious residential development in St Brelade, Jersey, Channel Islands.

The project remit called for a temporary works design to eradicate ground loss from surrounding property in order to safely construct a 1000m2 basement approximately 6 meters deep.

On submission and approval from the client’s engineer, this challenging project commenced. It entailed the installation of sheet piles driven to varying lengths up to 16 meters to act as temporary ground support during the excavation and completion of new basement structure.

In combination with the piles and prior to any excavation, upper level lateral propping in the form of a “Mega Brace” was installed to withstand the resultant force on the sheet piles during the ground reduction to basement level.

Given the close proximity boundary and the requirement to drive piles to 16 meters we opted to install with a Mobilram Telescopic thus providing flexibility and maximum driving efficiency through a state-of-the-art high frequency, low resonance system.

Brenwal also designed and installed a dewatering system through a series of ground water sump pumps. These were encapsulated in free draining sumps and water discharged through silt traps to a storm outfall.

The pump system remained in place until such time the basement structure and walls became watertight unaided by dewatering. Of further note the dewatering ensured the excavated sand remained dry throughout the excavation process.